C. Bamford, S. U. Mullik
Mar 1, 1976
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0
Influential Citations
19
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Journal
Polymer
Abstract
Abstract Tetrafluoroethylene may be polymerized in acetic acid at ambient temperatures and pressures close to atmospheric with photoinitiation by transition metal carbonyls, notably Mn2(CO)10, Re2(CO)10 and Os3(CO)12. A kinetic study of the reaction photoinitiated (λ = 435.8 nm) by Mn2(CO)10 is presented. The rate of polymerization is proportional to the square root of the incident intensity and the order in tetrafluoroethylene concentration is ∼1.4, over the range 0.78–2.60 mol l−1. The decay coefficient of Mn2(CO)10 is linear in C2F4 over the range studied (up to 0.45 mol l−1). These and other observations indicate that the dependence of the rate of initiation on [C2F4] in acetic acid is much less ‘sharp’ than in other systems examined. Occlusion phenomena are not marked under the conditions used. Polymers prepared in this way show the infra-red absorption near 2000 cm−1 characteristic of (CO)5MnCF2CF2—end-groups, confirming that the initiating radicals have the structure (CO)5MnCF2CF2. In our experiments no evidence of chain-transfer to acetic acid could be found, a result which we attribute to the polar properties of the medium and the propagating radicals. The polymerization is powerfully retarded by benzene, which enters into addition and H-abstraction reactions with the fluorinated radicals; a simple kinetic treatment is presented. Photoinitiation by benzoyl peroxide is shown to be accompanied by retardation. Tetrafluoroethylene may also be copolymerized with the aid of the present technique and some results with ethylene and vinyl acetate are briefly described. It is noteworthy that in the copolymerization of C2F4 and C2H4 chain-transfer to acetic acid has been detected.